This invention relates to a device for reversing the direction of motion of a paper sheet and more particularly to such a device capable of dependably reversing the direction of transportation of a paper sheet, independent of its material quality or shape.
Such devices for reversing the direction of motion of a paper sheet are recently coming to be used frequently in apparatus such as copiers, printers and facsimile machines. FIG. 1 shows an example of prior art paper reversing device 1 of this kind, disclosed in Japanese Patent Publication Tokkai 8-67390, provided with a passage 15 extending vertically between a pair of guide plates 14a and 14b for guiding a paper sheet vertically upward and downward. An upper driver roller 11, adapted to rotate in the counter-clockwise direction by means of a motor (not shown), is disposed at one end position (xe2x80x9cthe start positionxe2x80x9d) 15a of the passage 15. A paper-supplying follower roller 12 is pressed against the upper driver roller 11, and a paper-discharging follower roller 13 is pressed against the upper driver roller 11 from the opposite side, sandwiching the upper driver roller 11 with the paper-supplying follower roller 12. These two follower rollers 12 and 13 are adapted to rotate by following the motion of the upper driver roller 11. The combination of these three rollers (the upper driver roller 11, the paper-supplying follower roller 12 and the paper-discharging follower roller 13) is sometimes referred to as xe2x80x9cthe tri-roller.xe2x80x9d
At a position inside the passage 15 vertically below the tri-roller, there is provided another driver roller (xe2x80x9cthe lower driver roller 16xe2x80x9d) adapted to be rotated in the clockwise direction by means of another motor (not shown), and another follower roller 18 is disposed opposite thereto. The rotary shaft of this follower roller 18 is supported by a solenoid 17 such that the follower roller 18 is movable horizontally (to the left and the right with reference to FIG. 1) by this solenoid 17. When the follower roller 18 is moved by the solenoid 17 to the left, a gap appears between the follower roller 18 and the lower driver roller 16 for passing a paper sheet therethrough. When the solenoid 17 moves the follower roller 18 to the right, the follower roller 18 is pressed against the lower driver roller 16 and rotates therewith.
The front edge of a paper sheet 2 transported to the paper reversing device 1 is brought to the start position 15a of the passage 15 so as to be clamped between the upper driver roller 11 and the paper-supplying follower roller 12 and guided vertically downward through the passage 15. At this moment, the lower driver roller 16 is not activated and the follower roller 18 is retracted to the left by the solenoid 17, leaving a gap so as to allow the paper sheet 2 to pass therethrough.
After the front edge of the paper sheet 2 passes through the gap between the lower driver roller 16 and the follower roller 18, the follower roller 18 is moved to the right by the solenoid 17 such that the paper sheet 2 becomes clamped therebetween. Since the lower driver roller 16 is not driven yet, however, it is caused to rotate in the counter-clockwise direction by the downward motion of the paper sheet 2 (while the follower roller 18 is thereby caused to rotate in the clockwise direction). In other words, the paper sheet 2 continues to be transported downward inside the passage 15.
As the back edge of the paper sheet 2 passes the contact point between the upper driver roller 11 and the paper-supplying follower roller 12, the lower driver roller 16 starts to be driven by the associated motor, rotating in the clockwise direction and thereby causing the paper sheet 2 to reverse the direction of its motion and to move in the vertically upward direction inside the passage 15, while remaining clamped between the lower driver roller 16 and the follower roller 18. Thus, the upwardly moving paper sheet 2 is discharged out of the passage 15 from its back end while being sandwiched between the upper driver roller 11 and the paper-discharging follower roller 13.
In summary, the paper reversing device 1 serves to supply the paper sheet 2 downward into the passage 15 from its front edge, to reverse the direction of transportation of the paper sheet 2 after the supplying is completed (when its back edge is brought inside the passage 15) and to discharge it out of the passage 15 from its back edge by moving it upward. Such a mode of supplying and discharging a paper sheet by means of a tri-roller as described above, that is, the mode of using a driver roller and a paper-supplying follower roller to supply a paper sheet and using the same driver roller and a paper-discharging follower roller to discharge the paper sheet is commonly referred to as the tri-roller method.
A problem with the paper reversing device 1, as described above, is that the cross-sectional size of the passage 15 is large at its start position 15a where a tri-roller is disposed. As a result, the space for the paper sheet to pass through is large, giving rise to the possibility that the back end of the paper sheet 2 may not dependably move from the side of the paper-supplying follower roller 12 to the side of the paper-discharging follower roller 13 when the paper sheet 2 inside the passage 15 is about to be discharged. This probability increases in particular in the case of curled paper.
As explained above, furthermore, the paper sheet 2 which has been supplied into the passage 15 by means of the upper driver roller 11 and the paper-supplying follower roller 12 is guided downward through the passage 15. This gives rise to another possibility that the paper sheet 2 may undergo a free fall as soon as the back edge of the paper sheet 2 is released from the clamping between the upper driver roller 11 and the paper-supplying follower roller 12. This probability of free fall is particularly high if the paper sheet is thin or heavy.
It is therefore an object of this invention in view of the problems described above to provide an improved paper reversing device capable of dependably reversing the direction of motion of a paper sheet and discharging it independently of the material quality or shape of the paper sheet.
A paper reversing device embodying this invention for reversing the direction of motion of a paper sheet, with which the above and other objects of the invention can be accomplished, may be characterized as comprising a passage for guiding the paper sheet therethrough, a plurality of rollers each having a specified function and a guiding member for pressing and guiding a portion of the paper sheet in a specified direction for discharging. One of the rollers (xe2x80x9cthe first rollerxe2x80x9d) is a driver roller and its rotation causes the paper sheet to be supplied (in xe2x80x9cthe first directionxe2x80x9d) into and discharged (in xe2x80x9cthe second directionxe2x80x9d) out of the passage. Another roller (xe2x80x9cthe second rollerxe2x80x9d or xe2x80x9cthe paper-supplying follower rollerxe2x80x9d) is for contacting and rotating with the first roller and thereby transporting the paper sheet in the first direction into the passage. Still another roller (xe2x80x9cthe third rollerxe2x80x9d or xe2x80x9cthe paper-discharging follower rollerxe2x80x9d) is disposed on the opposite side of the first roller from the second roller such that the second and third rollers sandwich the first roller therebetween, and serves for transporting the paper sheet in the second direction out of the passage by contacting and rotating with the first roller. There is still another roller (xe2x80x9cthe fourth rollerxe2x80x9d) which is a driver roller disposed in the passage and serves to allow the front edge of the paper sheet to pass by when it is transported in the first direction by means of the first and second rollers. When the paper sheet has passed between the first and second rollers and its back edge has been disengaged therefrom, however, the guiding member functions to press and guide the back edge of the paper sheet towards the third roller and the four roller rotates so as the transport the paper sheet in the second direction and discharge it between and by means of the first and third rollers. In this manner, the direction of motion of the paper sheet inside the passage can be dependably reversed without regard to the material quality or the size of the paper sheet.
If the second roller and the guiding member are coaxially disposed so as to share a shaft as their common axis of rotation, their structures can be simplified. If the guiding member is designed to have a surface configured along the outer periphery of the first roller, the paper sheet can be more dependably guided towards the third roller.
The guiding member may be designed to press the paper sheet by its own weight, or by the gravitational force thereon. If the guiding member is made of an elastic material such that it pushes and guides the back edge of the paper sheet by its elastic force, the guiding of the paper sheet thereby can be effected more dependably.
The passage for the paper sheet may be preferably be designed such that the aforementioned second direction is sloped and makes a specified acute angle from the vertical direction towards the third roller. The paper sheet can then be discharged more smoothly. The angle of the slope is preferably selected to be equal to the angle made by the line which is tangent to both the first and third rollers. It is further preferable to design the passage so as to include a curved lower end part such that the paper sheet can be prevented from falling freely by its own weight inside the passage. The radius of the curvature of this curved portion may be varied according to the material characteristics of the paper sheet. This lower end part of the passage may be made detachable such that a jamming paper sheet can be removed easily. For example, the passage may be structured so as to be separable into a first passage part and a removable second passage part, connector members being provided to connect them. The passage may be formed by means of guide plates to make it openable for removing a jamming paper sheet.
A paper holder member may be disposed inside the passage for serving to hold the paper sheet so as to dependably prevent the free fall of the paper sheet in the first direction inside the passage.
A fifth roller may be further provided as a follower roller, disposed opposite the fourth roller for transporting the paper sheet in the second direction by contacting the fourth roller. An elastic member may be provided to support the shaft of the fifth roller to apply its biasing force on the fifth roller towards the fourth roller.
The fourth roller may be D-shaped in cross-section, having a straight line portion and an arcuate portion, such that the paper sheet can be passed by smoothly in the first direction when it is being supplied into the passage and transported dependably in the second direction when it is being discharged.
With a device thus structured according to this invention, each paper sheet is transported in the first direction by means of the first and second rollers but as soon as it passes through these rollers and its back edge is disengaged from them, the fourth roller begins to transport it oppositely in the second direction while its back edge is pressed and guided towards the third roller. Thus, the paper sheet is dependably discharged between the first and third rollers with the direction of its motion reversed.